Allogeneic Blood or Marrow Transplantation with Post-Transplantation Cyclophosphamide as Graft-versus-Host Disease Prophylaxis in Multiple Myeloma.

Allogeneic blood or marrow transplantation (alloBMT) may lead to long-term disease control in patients with multiple myeloma (MM). However, historically, the use of alloBMT in MM has been limited by its high nonrelapse mortality (NRM) rates, primarily from graft-versus-host disease (GVHD). We previously demonstrated that post-transplantation cyclophosphamide (PTCy) decreases the toxicities of both acute and chronic GVHD after alloBMT. Here, we examine the impact of PTCy in patients with MM undergoing alloBMT at Johns Hopkins Hospital. From 2003 to 2011, 39 patients with MM underwent bone marrow or peripheral blood alloBMT from HLA-matched related/unrelated or haploidentical related donors after either myeloablative or nonmyeloablative conditioning. Post-transplantation GVHD prophylaxis consisted of cyclophosphamide (50 mg/kg) on days +3 and +4 with or without mycophenolate mofetil and tacrolimus. Engraftment was detected in 95% of patients, with neutrophil and platelet recovery at a median of 15 and 16 days, respectively. The cumulative incidences of acute grades 2 to 4 and grades 3 and 4 GVHD were .41 and .08, respectively, and no cases of grade 4 acute GVHD were observed. The cumulative incidence of chronic GVHD was .13. One patient succumbed to NRM. All cases of chronic GVHD involved extensive disease and 60% of these patients received systemic therapy with complete resolution. After alloBMT, the overall response rate was 62% with complete, very good partial, and partial response rates of 26%, 21%, and 15%, respectively. The median progression-free survival was 12 months and was associated with the depth of response but not cytogenetic risk. The estimated cumulative incidence of relapse was .46 (95% confidence interval [CI], .3 to .62) at 1 year and .56 (95% CI, .41 to .72) at 2 years. At last follow-up, 23% of patients remain without evidence of disease at a median follow-up of 10.3 years after alloBMT. The median overall survival was 4.4 years and the 5-year and 10-year overall survival probabilities were 49% (95% CI, 35% to 67%) and 43% (95% CI, 29% to 62%), respectively. The use of PTCy after alloBMT for MM is feasible and results in low NRM and GVHD rates. The safety of this approach may allow the development of novel post-transplantation maintenance strategies to improve long-term disease control.